Machine-switching telephone-exchange system.



S. B. WILLIAMS, ln. & A.`B. SPERRY. MACHINE SWITGHING TELEPHONE EXCHANGE SYSTEM. APPLICATION mln MAR. 12.1911.

1,252,978. Patented Jan. 8, 1918.

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MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLlcATloN FILED MAR. 12,1911.

1,252,978. Patented Jan. s, V1918 4 SHEETS-SHEET 3- /m/en far 5am ue/ 5 Wfl/fama Jn 4r/har B. Sperry E S. B. WILLIAMS, 1a. 6; A. B. SPERRY. MACHINE swlToHyNG TELEPHONE EXCHANGE SYSTEM.

I APPLICATION FILED MAH. I2, i917.

E Patented Jan. 8,1918.

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UNITED lsfrATEs PATENT f oEEicE.

SAMUEL B. WILLIAMS, JB., OF BROOKLYN, ANI) ARTHR B..SPERRY, OF YORK,

N. Y., .t .SSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK,

N. Y., A CORPORATION OF NEW YORK.

MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented J an. S, 1918.

Application led March 12, 1917. Serial No. 154,183.

To all whom it may concern Beit 'known that'we, i MUEL B. VIL- LiAMs, Jr., and ARTHUR BQSPERRY, citizens of the United States, residing at Brooklyn, in the county of Kings and State of New York, and at New York, in the county of New York and State of New York, respectively, have invented certain new and useful Improvements in. Machine-Switching Telephone-Exchange Systems, of which the' following is a full, clear, concise, and exact description.

This invention relates to Amachine switching telephone exchanges of the type wherein a repeating relay at the central oiice is operated by a sender to transmit impulses to the stepping magnets to set the switches.

spouse of .the called party causing a circuit change to .be brought about to connect the condensers in circuit with the called line to complete the talking circuit.

Another;` feature-is the provision of a circuit arrangement wherein, when one of the selectors is set by the sender in operative relation to the vdesired trunk group, it

will not hunt in such group if all the trunks thereof are busy, but will be automatically set in operative relation to another group of equivalent trunks which it will then automatically test in succession. This is brought about in the present embodiment by an auxiliary switch mounted on the brush shaftyof the selector, and having anumber of metallic segments and a brush, which, in the primary movement of the shaft, cooperates with such segments.

segments is'provided for each trunk group which is likely to be overloaded. When all thetrunks of the group to which the segment belongs are busy, a characteristic potential is automatically placed V thereon. `After the bru'sh engages this segment "at the One of these termination of the primary movement, a circuit is closed to prevent the escape inagnet from passing the selector side switch to the trunk hunting position, as it otherwise would do, and a relay is operated by the closure of this circuit to transmit an additional impulse to the primary magnet of the selector to set the same in operative relation to the equivalent trunk group. The circuit through `the auxiliary switch is broken by'this additional movement` of the shaft, and denergizes the escape magnet,l

which releases the side switch into the trunk "hunting position to initiate the trunk hunting movement of tl'ie'selector..

Another feature relates to the arrangement for feeding current to the connected lines,- and is especially adapted for private branch exchanges employing automatic working. Then a call is set up `by one private branch subscriber withanother in the same private branch exchange, current is fed to both`lines from suchexchange andwhen aprivate branch exchange subscriber sets up a connection with the main office with which the private branch exchange isassociated, the bridge at the private branch exchange for feeding current to the calling lines is cut off and current is fed to such 'line from the main oijice.

Figuresl, 2, 3 and 4 when placed side by side with the circuits therein `ioining, show an established connection from the substation A, Fig. l to the substation B, Fig. 4.

The invention will be more readily under stood from a detailed description of the operation.

Upon the removal of the receiver at substation A, line relay 100 ,is energized. In

attracting its left armature it creates a calling condition upon the multiple 101 of sub station A in the finders in which such line appears. In attracting its right armature, it energizcs relay 10:2 to start a line finder `in search ot' the calling line.

Relay 10Q` in attracting its upper armature` locksitself to conductor 103, independently of the right armature and back con-4 tact of relay-104i, and in attracting its lower armature, applies ground to multiple seginen't 105 individual to the group of lines to which substation A belongs, and also closes the circuit of the primary magnet PM of the line. finder as. follows.: ground, lower .ai; mature 'and til-ont Contact `of relayi 102, conductors 106, 107, armature and back oniro y 121, 122overthe'multiples 123, 124 and 101,

tact of'rlay .108,eonaetorioaisiaaswach back contact of magnetP I free pole of battery. `This magnet'makes and breaks f its own circuit, thus rotating the finder brush shaft 153. The attraction of the lower armature of relay 1 02 also closesa circuit for relay 111 in parallelwith that traced for magnet PM: ground, lower armature and front contact of relay 102, conductors'106 and 107, armature and back contact of relay 108, conductor 113, relay 111, free pole of battery. Relay 111 `connects the group brush-114 to the escape magnet ESC. At this time, however, the escape magnet does not operate since it is shunted over the path traced includin the armatureand back contact of magnet M. .Magnet PM' energizes in the circuit traced and near the end of its Astroke opens the shunt about the escape magnet, at which time the brush 114 is in contact with grounded group segment 105 andbecomesenergized over the followip circuit: freepole of battery, magnet P magnetESQconductor 115, `left armature andsfront vcontact of'relay- 111, conductor i1165fbrsh.114,'segment 105, to ground at'the lowexarmature'and'front contact of relay the escape magnet is maintained energized 102.5` The escape magnet is constructed tov re- :leasevthe side switch lfrom position 1 to position -2 uponA its nergi'zation. In position' 2,

over'the followii circuit: free pole of battery;- magnet P magnet. ESC, armature and back contact of relay 117, arm 118 and `its second'contact, conductor 119, conductor 200,201, left: armature and back con/tact of relay 202to ground. In lposition 2, arm 110;closes thefollowing circuit for magnet SM to stepthe positioned finder brushes`120,

ofthe giron to which substation A belongs: freepo e o battery, magnet SM, its armature and-backcontact, armature and front contactfof-magnet ESC, arm 1-10 and its second: Contact, conductor 109, to ground. at the lower. armature and 'fro-nt contact of relay 102. When the test brush 122 reaches the multiple 101 of substationA, the following circuit is vclosed to operatev test relay 117 to stop the movement of the line finder: free circuitof magnet SM to stop the the calling line terminals. Magnet ESC, in

pole of battery,resistance125, left armature and front contact of relay 100, vconductor 126, multiple'lOl, brush 122, relay 117 to ound. Rela 117 o ens the circuit traced or magnet E C whic 'becomes denergized, and in' retracting its armature, o ens the nder on d'energizing, releasesthe sidey SW into position 3. In position 3 arm 118 energizes the cut-off relay 4127 over the following circuit:

free pole of battery, right or'both windings of relay 127, depending upon -whether 4the substation -A isa restricted or a non-restricted` line, asgwill hereinafter more fully appear, conductor 128, contact 101, brus' 122, arm 118 and its third Contact,r conduc- `torsj119, 200, 201, left armature and backy contact 'of relay 202y to ground. Rela 127 in operating, denergizes relay 100. T e retraction of the left armature of relay 1'00 removes the calling condition from multiples 101 of substation. A, and the retraction of.

the right armature denergizes relay l102.

Relay 102, inretracting its lower armature V removes ground from starter'wire 107 an restores the continuit of the in-st'arter wire 129, 107. Relay 117 is shunted and becomes inert due t0 the application of thedirect ground to the brush' 122, referred to. In position 3 the following circuit including the calling line is'closed for the impulse relay 131: free pole of battery, .right winding 4of relay 131, conductor 132, arm 133 and itsV .third contact, conductor 134, arm 135 and its third contact, brush 121, terminal 124, through the telephonie apparatus at substation A, terminal 123, brush 120armg 136 and its thirdcontact', conductors 137, 138, left Winding of-relayv131, ground. Relay 131, in operating,energizes aslow relay 139;- Relay 139, in attracting its right armature, interposes a breakin the circuit of finder -release ff'nagnet RM. In attracting its left armature, this relay closes the 'following circuitto energize a slow relay202 (Fig. 2); ground', lert armature and front contactv of 'relay 139, conductors 140, 2'03, 204, first selector side-switch .arm 205-, relay 202, free pole of battery. Relay`202, in attracting its left armature, closes the following circuit for relay 206 which in operating, connects the primary magnet PM tact of the stepping relay 131. When the inder side switch moves into position 3, a

' distinctive tone is transmitted over the following circuit to -the calling line to indicate to the calling party that the central oflice apparatus is ready to receive impulses: free-pole of-battery, secondary winding'223 of tone source 224, relay 218, conductor 222, left armature and back contact of relay 221, conductor 220, arm 219- and its iirst contact, lower. armature and back contact of relay '209, conductor 225, right winding of relay 208, free pole of battery. This tone is transmitted by induction through the windings of relay 208 to the calling line over the follow ing circuit: ground, left lwinding of relay 208, conductor 226, upper talking conductor 227, condenser'269, conductor 144, arm 136 to the backl conl" and its third contact, brushV 120, terminal .123, through the telephonie apparatus at substation A, terminal 124, brush 121, arm

V135 and its third contact, conductor 134,

arm 133 and its third contact, right'winding of relay'131, free pole of battery` The calling party now operates his sender S retransmit the first digit of thelwanted number. In returning to normal, the sender VVAinterrupts the circuit traced a number of times, corresponding to the digit involved. Uponeach retraction of the armature of relay 131, an impulse is -transmitted over the following path: ground, finder primary offnormal contact PON, armature and back contact of relay 131, right armature and front contact of relay 139, arm 142 and its third contact, conductors 143, 207 (Fig. 2), left armature and back contact of relay 208, slow relay 209, arm 210 and its rst contact, conductor 211, left armature and front contact of relay 206, magnet PM, free pole of battery. Magnet PM, in response to these impulses, steps the se-v lector brnthes 212, 213, 214- into operative relation with theV desired group of trunks 215, 216, 217. Relay 209, being slow to release its armatures, is maintained energized during the transmissionl of the impulses. this relay'closes the following circuit for a i relay 218: ground, lower armature and front contact of relay 209, arm 219 and its first Contact, conductor 220, Kleft armature and back contact of relay 221, conductor 222, relay 218, free pole of battery. Relay 218, in operating, closes the iollowing'circuit for the escape magnet 228 of the first selector, which magnet is constructed to release the sidel switch from position to-position upon its denergization: free pole y of battery, magnet 228, arm 229, conductor 247, spring 248 andarmature of relay 218 to ground.

When the sender S' restores and maintains relay 131 energized, relay 209, after a-'slight interval, becomes denergized, opening the circuit of relay 218, which, in denergizing opens the circuit of thel escape magnet 228, which, inreleasing its armatures, passes the side switch to position 2 to initiate the trunk hunting operation. Inposition 2,l escape magnet 228 is again energized over the following circuit: free pole of battery, magnet 228, arm 229` and its second contact, spring 230, now closed to its lower contact to ground. Magnet 228, in attracting its arma.-

ture, closes a self-interrupting circuit for the secondary stepping magnet SM of the `first selector: free pole of battery, magnet SMQ its armature and back contact, armature and front contact of magnet 228, arm 231, conductor 232, left armature and back contact of first selector release magnet RM` armature and back contact 0i' relay 221,V conductor 233, left armature and front contactV of relay 202 to ground. Magnet SM thus steps brushes 212, 213, 214, over the selected group in searchof an idle trunk. Test multiples 217 of busy trunks are grounded, as will hereinafter appear. Upon the first seeondary step ofthebrushes, contact 230 is opened and the escape `magnet is dependent for'. its continued, energization upon 7 tl` In attracting its lower armature,l

grounded condition of its test multiple 217 causes the denergization of theescape magnet, which opens the stepping circuit, thus stopping the selector upon suohtrunk, and in denergizing passes the side switch to po sition 3.

In position 3l ground is supplied to the test multiples 217 of the seized trunk over the following circuit: brush 214, conductor 236, arm 237 and its third contact, right armature and front contact of relay 202 to ground. The application of this ground energizes a relay 300 in theA connector (Fig. 3), which, in attracting its outer right armature, connects primary magnet P2M2 of the connector to theupper ,talking conductor 301 to receive the tens impulses, and in attracting its `left armature, interposes a reak in the circuit of the connector release iagnet R2M2. The calling party now operates his sender S to transmit the tens digit of the wantednumber. Upon each retraction of the armature of the stepping relay 131, an' impulse is transmitted over the following circuit to the primary stepping magnet PM2 of the" connector: armature of relay 131 now grounded, and its back contact, right armature and front `contact of relay 139, arm 142 and its third contact, conductors 143, 207, left armature and back contact of relay 208, relay 209, arm 210 and its third contact, conductors 234, 243, 145,

arm 146-and its third contact, conductors 147, 235, brush 212, terminal 215., conductors 301, 302, outer armature and front contact of relay 300, arm 303 vand its first contact, magnet WMZ, free pole of battery. Magnet P2M2 thus steps the brushes304, 305, 306 into operative relation with the group of terminals containing those of the wanted line 307., 308, 309. The slow relay 209 in the circuit traced for the primary magnet, became energized upon the rst impulse, and remained energized during the trans mission of theimpulses. In attracting its lower arl'nature, this relay closes the following circuit for the escape magnet 310 of the connector, which releases the connector side switch from position to position upon its de-` energization: ground, lower armature and front contact of relay 209, arm 219 and its third contact, conductors 238, 148, arm 149 and its third contact, conductors 150, 239, brush 213, terminal 216, conductors 311, 312, arm 313upper armature and back con- 4tact of relay 314, escape magnet 310,V free pole of battery. lVhen the sender restores and maintains impulse relay 131 energized, the slow relay'209, after a slight interval,

becomes inert, opening the circuit traced for magnet' S2M2 substitutes the secondary magnet S2M2 for the primary magnet P2M2 in the stepping circuit. The calling party now operates his sender. l to transmit the units digit of the wanted number. Upon each retraction of the armature of relay 131 an impulse is transmitted over the circuit traced to the side-switch arm 303, thence to the secondary magnet S2M2, free pole of battery, and as be'forev the slow relay 209, in attracting its lower armature, energizes the connector escape magnet 310 over side switch arm 313 and now by way of its second contact. The steps the brushes 304, 305, 306 into engagement with the multiples 307, 308, 309,0f4 the desired-line. If the vline is busy'its test terminal 309 will be grounded over a brush 306, arm 316 and its third contact, and the left grounded armature of the relay 315, or such arm and its fourth contact and the right-hand low-resistance windin of the relay 315 to ground. In such event tiie left-hand high-resistance winding of relay 315 vof, the testing con nector 1s shunted and Vdoes not attract its armatures. In passing out of position 2 con- .4

nector side-switch arm 317 opens the circuit of relay 300. -This relay .thereupon becomes inert', and in retracting its left armature, closes the Acircuit of connector release magnet RZM2 as follows: free pole of battery, magnet RQM, conductor 318, left armature andback contactof relay 300, primary off-normal contact 319 to ground.

The release magnet in energizing restores.

the connector to its normal position and also restores the side switch.` Before contact 319 opens, however, as theV brush shaft is restored, contact 320 closes, which results in a locking circuit being provided for magnet R2M2 as follows: free pole of battery,

magnet-R2M2, left armature and back contact of relay 300, conductor 321, contact 320,

' resistance 322, conductor 323, right armature and front contact of magnet R2M2., release conductor 325, terminal 217, brush .214, conductor 236, arm 237 and its third contact, right armature and front contact of relay 202 toground. Magnet H2M, at its left armature and front contact, closes the following circuit to produce a busy tone in the calling line to indicate to the calling party that the line desired is occupied: ground,l secondary winding of source of busy tone current 326, left armature and front contact of magnet R2M2, arm 327 and its first'contact, condenser 328, arm 329 and its first contact, conductors 330, 311, terminal 216, brush 213, conductors 239, 150, arm 149 and its third contact, conductors 148, 238, arm219vand its third contact, lower armature and back contact of relay 209, conductor 225', right winding of relay 208, free pole of ,/battery. An induced current is created inthre secondary .winding-.of relay 208 included in the calling circuit. This circuitis the same as that traced for Athe dial tone. The calling party, upon hearing this busy tone, replaces his receiver. VThe replacement of the receive` denergizes relay 131, which, in retracting its armature, opens thev circuit of slow relay 139. This relay after a slight interval releases its arma.- tures. The retraction of the right armature closes the circuit of finder release magnet RM as follows: free pole'of battery, magnet RM, conductor 151, right armature and back contact of relay 111, conductor 152, right armature and back contacts of relays'139, 131, contact PON to ground. The release'rnagnet, in addition to restoring the linder brush shaft 153,

energizes relay 202. Relay 202, in .retracting its left armature, b'pens the circuit of relay 206, which relay, in'retracting its right armature, closes the circuit of irst selector release magnet RM. as follows:-

free pole of battery, magnet RM, right armature and back Contact of relay 206,

contact PON to ground. "Magnet RM, in addition to restoring the selector brush shaft, also restores the side switch. lVhen -the shaft reaches its 'normal position, contact POM opens and denergizes the magnet RM. The retraction of the right armature of relay 202, removes'ground from ,`conductor 236 which results inthe denergization of connector release magnet R2M2. The apparatus is now all restored.

Assuming the selected line to be idle,lfull potential is present upon the multiple 309. thereof, and the test relay 315 becomes energized over its left-hand high resistance winding, in the third position of the side switch. VThisl circuit is as follows: ground, left winding of relay 315, arm 316 and its third Contact, brush 306, terminal 309, cutoff relay of the selected line, free pole of battery. Both the cut-oil'l relay and the relay 315 become energized in this circuit, the former removing the control of the line relay from the selected line in the. well-known manner and the latter connecting the test multiples 309 directly to ground over yits left armature to cause the selected line to testbusy to other'connectors. The attrac-A tion of-the right armature of relay 315 maintains a slow relay 331 energized over the following circuit, this relay having been energized in position 2 over connector sideswitch arm 332,'.in parallel with thecscape' magnet 310: free pole of battery, relay 331,

- as.follo,ivs: free pole ofb'attery, relay 4300,-

I maintain such line busy.

its right armature and front Contact, conductor 333, right armature and front contact of relay 331 to the grounded third wire 325.' This circuit is closed before the cir cuit including the arm 317 and its second contact is opened, as the side switch passes out of position 2. Thus the relay 300 holds its left armature attracted to maintain the connector release circuit open. In parallel witlrthe relay 331 the escape magnet 310 is energizedto apply ringing current to the Iselected line. This circuit is as follows: free pole of generator 334, ringing cut-ofi' relay 314, inner armature and front contact ol? magnet 310, arm 335 and its third contact, brush 305, terminal 308, bell 336, terminal 307, brush 304, arm 337 and its third contact, outer armature and front Contact of relay 310 to round. A' portion of the ringing current ows over the following circuit to indicate by a characteristic tone to the calling party that the selected line is being signaled: free pole of generator 334, relay 314, inner armature and front contact of magnet 310, conductor 338, arm 327 and its third contact, condenser 328, arm 329 and its thirdcontact, conductors 330, 311, terminal 216, brush 213, conductors 239, 150, arm 149 and its third contact, conductors 148, 238, arm 219 and its third contact, lower armature and back contact of relay 209, righthand winding of relay 208, free pole' of battery. This tone is transmitted by induction through the windings of relay 208 to the calling line as before described.

When the called party removes his` receiver, marginal ringing cut-off relay 314 becomes eneigized, opening the circuit of escape magnet 310 which, in deuergizing, passes the side switch to position 4. In position 4 arm 316 connects the test multiples 309 to ground through the low-resistance right-hand winding of test relay 315 to Arm 332, in passing out of position 3, opens the circuit of slow relay 331. Before this relay -retracts its right ar iature, however, arm 317 reaches position 4am] connects release relay 300'to the grounded thu-d conductor 325 to prevent premature release. The arm 329 reaches its fourth contact before the right armature of relay 331 is retracted, which results in an impulse being trai'ismitted over the following circuit to energize the called supervisory relay 208: ground,left armature and front contact of relay 331, arm 329 and its fourth contact, conductors 330,311, terminal 216,

brush 213, conductors 239,150, arm 149 and4 its` third contact, conductors 148, 238, arm 219 and `its third contact, lower armature and back contact of relay 209, conductor 2253, right winding of relay 208, free pole of battery.. `Relay 208in attracting its. right armature, closes the following circuity for the. first selector escape magnet 228:

ground, right armature and front contact of said relay, conductors 246, '240, left ar,- mature and back contact of relay 241, conductor 242, arm 229 and'its third contact, magnet 228, free pole of battery. When the impulse ceases and relay 208 retracts its right armature, the escape magnet, in releasing its armatures, passes the side switch to position 4, in which position the called supervisory relay 208 is energized over the called linecircuit as followsfree pole of battery, right Winding of relay 208, conductor 225, lower armature and back contact of relay 209, arm 219 and its fourth contact, conductors'238, 148, arm149 `and its third contact, conductors 150, 239, brush 213, ter minal 216, conductor 311, arm 335 arid its fourth contact, brush 305, terminal 308, through the telephonie apparatus at substa tion B, terminal 307, brush 304, arm 337 and its fourth contact, conductor 301, terminal 215, brush 212, conductors 235, 147, arm 146 and its third contact, conductors 145,` 243, arm 210 and its fourth contact. arm 244, conductor 245, left Winding of relay 208 to ground.' Relay 208, in attracting its left armature, permanently interposes a break in the impulse circuit to prevent the calling party vfrom thereafter transmitting impulses to the magnets, and in attracting its right armature, closes a substitute circuit for slow relay 202 as follows: ground, right armature and front contact of relay 208, conductor 246, arm 205 and its fourth contact, relay l202, free poleof battery. Since relay 202 the called line over the windings of relay 208.

Upon the termination of the conversation and the replacement of the receiver by the calling party, the finder is released asalready described. The replacement of the receiver by the called party denergizes relay 208, which, in retracting its lright armature, opens'the circuit of relay 202. The retraction of the left armature of this relay denV ergizes relay 206 as described in connection with a busy call, the denergization of this relay causing the release of the first selector. The retraction of the rightarmature of relay 202 removes ground from the third wire 226, with the result that relay 300 becomes inert, and at its left armature4 and back` contact closesfthecircuit of release magnet R2M2 of 'the connector as described in connectionr trol of the sender S in operative relation to a group of trunks terminating in jacks 400 at the distant office (Fig. 4). The operations are the same as those traced up to the point where the selector brushes are set, except that a brush 251 (fixed to the selector shaft 252) at the end of the primary movement of the selector shaft rests in contact with a segment 8, instead of one of the segments 1 to 6 inclusive belonging'to trunk groups terminating in ,connectors having access to locall or lines in the private branch exchange. When the selector side 4switch passes to position 2 at the termination of the primary setting movement, a relay 241'is energized over the following circuit: free pole of battery, relay 241, armature and back contact of 'relay 262, arm 254 and its'second contact, seg'- ment 8, brush 251, conductors 250, 265, arm 237 and its second contact to ground at the right armature and front contact of -relay 202. Relay 241 in operatin locks itself to rounded conductor 203. pon the seizure of the trunk in the outgoing oup selected, the following circuit is closed-:r free pole of battery, relay 401 (Fig. 4), conductor 402, relay 403, conductor 404, terminal 217, brush 214,' conductor 236,` arm 237 and its third l contact, the right armature of relay 202 to ...ginal an series-with both 'windings 'of '55 energized, and'in attracting its upper armaground. Relay 403, in attracting its-upper armature, opens the bridge across thetalking conductors including the condenser '450, and in attractingits lower armature, lener- `zes Vrelay 405 over ltll'e following circuit: ree pole of battery, relay 405; conductor 406, lower armature and' front contact of relay 403, lowerarmature andback 'Contact of relay 407 to ground. Relay 405, in attracting its lower armature, connect-sboth .windings of relay 408 in series to the lower talking conductor 409 .towhicli is connected the right winding of thecalled supervisory relay 208. This circuitv is as follows: ground, windin of lrelay 408 in series, armature and bac contact of relay 410, lower armature and ront contact of relay 405, conductor 409,

terminal 216, brush 213, conductors 2349, 150,v

arm 149 and itsrthird contact, conductor- 148,

conductor 238, arm 2191and its third :,contact,

lower armature andrb'ack-:contactfof 'relay 209, conductor .225, 'right ,winding of relay 208, free pole of-batter'y. "lel'ay 208 ismardoes not attrae. .'armaturesin e'lay408 when this-circuit is closed, ,"but it,h'e`"relay 408 is "ture, energizes' the relay 411. -Relay 411 in turn energizes relay 412 which, in attracting its armature 414, closes the following circuit to energize calling `supervisory relay 413 at the distant oilice: ground,` armature 414 of relay 412, spring` 415, conductor 416 leading to the distant oice, conductor 417, outer armature and back'contact f cut-0E relay 418, left. winding of rela-y 1413, free Role of'batthe plug and ground tothe 'lower'tallii'ng conductor at the lower armature and contact spring 424 ofwelay 412, relay 421 is loperated over the following circuit: free-pole of bat- `tery, answering-supervisory relay 422, ring of the plug, ring of the jack, conductor'423, left winding of relayl 421, spring 424, "lower armature of relay 412, resistance 425 to ground. The insertion of the plug .energizes the cut-olf rela 418 to 'denergize the line relay 413, whic in retracting lts armature, extinguishes lamp '419. Relay 421 becomes .energizedin the ,circuit traced, and in attractin its armatures, energizes relays 426 and 42 Rela 427, in operating, energizes relay 428, whic in Aturn operaties slow relay 429. Relay' 429, in operating, energizes relay'407. Relay 407, m 'attracting its lower armature, grounds -the thirdwire 404 leading back tothe selector and shunts out highattracti'ngfit's riglitfarrnature, closes the-following clrcuit .for-a relay 1258 "ground,`right armature and iront coritactof relay'208, .conductors 246,240,1 eft mature and springs 256,259 afi-15? 4,1 'e6-d trcting' tslefb ail'atu lo thirdl i ture and spring 256, conductors 257, 154,115,

magnet ESC, magnet PM, free pole ojf bat: tery. The: escape magnetvis constructed to release the side switch from position 3 to position- 4, upon its energization. As the arms 13 5 .and 136'- pass olf their third con- "tacts the calling supervisory relay 131 becomes inert, and after aslight interval, slow relay 139 releases its armatures. Release' of the finder does not occur, however, 'since arm I110 in position 4ext I'nds the conductpr 261, 1\ow grounded at t e right armature and' frontv 'contact o f relay 258 `to ther'elay.111,

and this relay becomes energized over the2 following'circuit: free pole of battery, relay 111, conductors 113, 109, arm 1,10: and its fourth contact, conductors 155, 156', conduc tor 261 to ground at the right armature and frontv contact of relay 258. Relay 111 in attracting its right armature interposes a break in the circuit of finder release magnet- PM, thisbreak being introduced before the relay 189.1'etracts its, right armature. The

actor 26mrelay e236, now grounded, as 'describedl atthe: lower armature and front contact of retraction of the left amature of relay .139 removes ground from conductor 203, thus denergizing the slow relay '202, but before this takes place, the rightarmature o f relay 258 has already applied a substitute ground to conductor 261, thus holding up the first selector' release relay 206, which is maintain-l ino` a break in the circuit of release magnet at its right armature and back contact. i The control of the release of the switches is now with the operator. erator plugged in and caused the energization of relay `407, as described, this relay, in addition to grounding the third wire leading back to the selector and shunting out the 'high-resistance winding of relay 408, opened the circuit of `relay 405 which restored the continuity of `the talking conductors. Upon the short-circuiting of the high-resistance winding of relay 408 and the resultant advancement of the finder side switch to the fourth position, the circuit for relay 408 became opened, and this relay, in retracting its upper armature denergized relay 411, which in turn denergized -relay 412. This relay, in retracting its armatures, completed the talking circuit. Upon the retraction of armature 455 of relay 412, the circuit for av relay 456 is opened. This relay was energized upon the operation of relay 412. Relay 456 does not release its arma.- ture until after springs 424 and 415 have reached their back contacts.` Thus thecondenser 450 is bridged across the vtalking conductors 433 and 409 momentarily, to prevent the calling party from getting a disagreeable click in his ear.` During conversa tion, relays 426, 427, 428, 429, '431 and 410 are energized. Relay 426, in attractingr its right armatune, closes a noneinductive shunt around the left winding of relay 421 to remove the impedance of this winding from the talking circuit. The operator by means of her head set (not shown) now com1nunicates with the calling party at substation A, talking current being supplied from the main oi'lice over the following path: free pole of batteryplower lefthand winding of repeating coil RC, relay 422,ring of the plug, ring of the jack, comluctor 423, right armature and front contact ofrelay 426, right-hand non-inductive winding of relay 421, spring 424 of relay 412, conductor 4,32, lower armature and back contact of relay 405, conduc` `tor 409, terminal 216, brush 213, conductors 239, 150, arm 135 and its fourth contact, brush 121, terminal 124, through the telephonic apparatus lat substation'A, terminal 123, brush 120, arm 136 and its fourthcon-y tact,.conductors 147, 235, brush 212, termi# nal 215, conductor 433,'upperarmature and back contact of relay 405, spring 415 yof relay 412 and itsbackv contact, conductor 416, tip of the jack, tip of the plug, upper left-hand winding of the repeating coil RCto ground.

When the opy Having ascertained the wanted number,

the operator inserts the plu 434 into jack 436l at substation B thereof by means of her ringing key,'not shown. `Upongthe response of the called party, the calling supervisory relay 437 operates and shunts out the calling supervisory lanrp 438 to indicate such response to the operator. As this part of the` circuit. is well-known, it will not 'be described in detail.

The replacement of the receivers bythe parties results in the denergization of the 435 of the desired line, an rings the bell supervisory relays 422, 437, and the illurnination of lamps 439 and 438. The replacement. of the receiver by the party at substa-l tion A, denergizes relay 421, which in turn` denergizes relay 426. Before this relay has retracted its left armature long enough to denergize slow relay 427, the right armature of such relay has reachedk its back contact, tl'ius'closingithe following locking circuit for yrelay 428: free pole of battery,

lower left-hand winding of repeating coil RC, relay 422, ring of the jack, ring of the plug, conductors 423, 440, right-hand armature and back contact of relay 426, upper armature aud front contact of relay 428, up-

` per winding of said relay, conductorsv 441,`

416, tip of the jack, tip of the plug, upper left-hand winding of repeating coil RC to ground. This relay is thus maintained energized after the retraction of the armature of .relay 427, and at its lower armature and front contact maintains relay 429 Aenergized, which in turn holds relay 407 energized, which relay, in maintaining'its lowerarmature attracted, holds ground on the third wire 404 leading back to the selector and Ifinder to prevent their release. yInre` sponse to the illumination of lamp 439, the

operator withdraws plug 420 from jack 400; thus denergizing relay 428, which, in retracting its lower armature, denergizes relay 429 which, in turn, in denergizing, renders relay 407 inert. The retraction of the lower armature of this relay removes ground from the third wire leading back to the -preceding switches, thus denergizing relay 258. yRelay 258, i'n reti-acting its right armature, removes ground from conductor 261, whereupon relay 206 becomes denermoval of ground from conductor 261l also denergizes relay 111 of the finder, which closes the circuitof finder releasemagnety RM hereinbefore traced. All the apparatus is now restored.

gifted, closlng,r the circuit of selectorI release `magnet RM as already described; AThe recircuit beingopened at the upper armature t of relay '407.' Relay- 405, in operating,

of relay 407. .Relay 407, 'when energized as theplug was inserted, prepared, at its upper armature and front contact, a circuit for-a slovvv` relay 431, which was closed when relay 408 released its lower armature as the finder side switch moved out of its third position. Relay 431, inA attracting its right armature,- applied an additional ground to thethird Wire 404 leading back tothe preceding switches, and at its left armature, energized relay-410- to connect relay 431 to the front contact lof the relay 405. When relay 407 releases as the plug is withdrawn,

its lower armature reaches its back contact and energizes relay 405 before the relay 431 has time to retract its right armature,rits

bridges this slow relay 431 across the call-4 4"ing line,-anddue to the closed condition of the-substation circuit at this time, becomes energized over the following circuit: free pole of battery, relay 431, relay 442, arma- `ture and front contactof relay'410, lower f armature and front contact of relay 405, conductor 409, `over the circuit previously traced including the` telephonie apparatus Aat substation A, returning over conductor 433, upper armature yand front. contact of relay 405, to ground. The relay 442 ener gizes relay 411, which in turn energizes reay 412. Relay 412 again closes the circuit f'traced'for the left Winding of relay413,

which, 'in -operating, again illuminates the lampA 419. This indicates to-the operator that the calling lpartyy desires. attention.

Referring now to Figs'. 2 and 4, each 'of the trunks '215, 216 and, 217 of tbe group leading tothe main oiiice to 'which group segment 8 belongs, is provided with a relay 401 (Fig. 4). `When 'a trunk of this group is seized, the4 relay 401 thereof becomes energized as described. If, at the termination of the hundreds set of impulses, that is, when the` selector is set .in operative relation to this group, all the trunks thereof are busy,` a circuit will be closed, including the `armaturesand front contacts of all the relays 401, 443, etc., in series,.,to maintain the es\ cape magnet 228 of the first selector in` its;

first position, and to cause an additional impulse to be delivered tothe irst selector primarv magnet PM, which will step the Y" .brushes 212, 213, 214 into operative relation to an equivalent trunk group; that is to say, to another group of trunks terminating in the same main roilice. The circuit l for the escape magnet is as' follows: free pole of battery,- magnet 228, arm 229 and ,its first contact, conductor 247 make-beforebreak contact 248 ofrelay 218, relay 249, conductor 250, brush 251 on the selector brush shaft 252, segment 253, arm' 254, conductor 255, through the left armatures and front contacts of relays 401,443, etc., in series of the selected group to ground. The closure of this circuit, in addition to maintaining the escape magnet energizedafter the armature of relay 218 is retracted as the impulses cease, also energizes relay 249 which, in attracting its armature, transmits an additional impulse to magnet PMv of the rst selector. The brush 251 is thus stepped ofi' the segment 253, opening the circuit traced for magnet 228 and relay 249.

Magnet 228 thereupon releases its armature,

passing the side switch to positionv 2 or the ltrunk hunting position. The trunk huntwing. operation then ensues as hereinbefore described'. r A

If Iall the trunksfof the-auxiliary group are busy, relay 221 will be energized td apply a busy tone tothe calling ,line when the selector leaves the last trunk terminal, due to the 4closure of'contact 271, this co1i-l tact being closed by the selector shaft when it takes ten and one-half steps. In attracting its right amature this relay'opens thev circuit of release relay 206, which in deenergzing closes the circuit of release magnet RM. Magnet RMin operating restores nects thelower 'talking conductor to the front contact of the left armature of relay 221 to which a busy-tone source'270 is connected. When rela-y 221 operated it locked itself to conductor 233, and. since this conductor is grounded at the left-amature and front contactv of relay 202, busy tone is maintained applied to the calling" line until thereceiver is replaced, whereupon release ,takes place as describedin connection with 'a busy call. This` relayis operated upon the tenth and a half-secondary step, while hunting in any group. f Q `f In thepres'ent embodiment of the inventhe side switch, and arm 219 .thereof conicoY tion, segments 1 to 6 inclusivel'are apporsl tioned to trunkV groups-local tothe private branch exchangeas stated, terminating in automatic switches, as shown' in Fig.3. Segments'8 and 9 are apportioned -tofthe trunk roups leading to the main ofiice toy SegmentsA 7 and 0 may be apportioned to ftrunk `groups terminating at other manual oiiices. It iwill be noted that when the selector-fis A'set yon the trunk groups tozwhich these Y,segments are apportioned,` the relay -241 is perated to prepare circuitsfor. cutting oi the local `bridge and feed current to ,which t is private .branch exchange belongs. f

the calling line fromthe-operators cord cir.` cuit, j as` described. --Oe of these trunky groupsmay lead to operators positions in the private branch exchange andthe other -v l v I to outside private branch exchanges.

It is desirable in private branch exchange l working-to restrict some of thefsubscrbers to-,local service, and the circuit arrangement of this invention is silch that when such ,a subscriber attemptsfnto set up a ina the relay2tl2 is as follows: free pole of longs, thc circuit ol battery, iri,f:, 'ht-hand winding of relay 127, 'conductor 128, terminal 101, brush 122, arin 118 and its third contact, conductors 119, 200, relay 262 toA grtuuid. This path leading throughthe right-hand winding of relay 127 is of such resistance that the current flowing 'therethrough and in series through relay 262 .is suflicient to energize vthe latter. When the slow relay 209 releases its armature, upon the tcrmiluition of the first set ot' impulses, and the side su'i tch moves into position 2, the grounded right-hand arinaturc of relay 202 is extended over firstV sc lector side-switch :i1-m28?. conductors 265 250, brush 251, segnicnt253, With which it is now in contact, arm 2?-1 and it-s second Contact, armature rind liront Contact of ,re lay 262, conductors 261, 263, release magnet RM, free pole ot battery. The ,tirst sclector is thus released when a restricted sub scriber attempts to set up a prohibited connection. Iii the calling party sets the selector brushes in operative relation to the extra trunk group to which segment 9 bethe release magnet is closed as described except that it leads from brush 251 to conductor 207 and thence to the front contact of 4relay 262.

The jack 44a is provided ior use in toll l calls. A party in thcprivate branch eX- ehangc, having called the operator at the main ollice (Fig. al), as descriln-al, and after having informed her of the toll connection desired, hangs up his receiver. r["he operator then Withdrawsthe plug -l20 from the jack LL00, and the eoiinection is broken down. lVhcn the toll comieetiou is set up, the operator inserts the plug 420 into the jack l0() lo light .lamp L145 bc re an operator at the private branch exchange. This is accomplished as follows: The operator inserts the pfui and operates her ringing key nlil-8, to close circuit to energize relay 421 as tolloivs: ringing generator 449, key l'1484, tip of the plug, tif) et' the jack, conductor 416, spring 415 o.. relay i12 and its back contact, upper armature and baclr contactA ot relay 1v'105, condenser 450, conductor 451, upper key 448, ringing generator e149. Relay. n121, in oi'ierating,

energizes relay L26 which in turn energi'. .s rela;i 12T. Relay 12T ii1.'o]1)crating energixca relay 128. Relay 428 attracts 'its upper armature. When the key isreleased relay -lll'-I retracts its rightv armature before relay 42T rctraets its armature, andconsequently the relay t28 is locked vover thocircuit proviously described, including the operatol"s` cord circuit. Relay' 428, in attracting its lower a rinatnre, energizes relay 4146 over the following circuit: ldwer grounded armature ot relay 128, conductor 5H?, right armature and Vback contact of relay 401, relay` 446, tree pole of battery. Relay. 116 locks itself to ground at the armature and back contact of relay 452, and lamp 445 is lighted over the tollmving circuit: free pole of battery. lamp l-il, conductor 153, lower armature and front contact of relay 446, armature and back contact of relay to ground. Relay 14:6 inA attracting its upper armature, operates relay #L01 and grounds the `third conductor i045 leading baci; to the selector (Fig. 2) .to render this trunk busy. Relay 403 is shunted at this time and remains inert. The operator at the private branch exchange now in,

.serts a plug int-o the jack 444i. The insertion o't' the Relay 446 in retracting its upper armature removes the shunt from about relay 403 and this r`elay becomes el'iergized over the following circuit: free pale of battery, relay 401, conductor 4,02, .relay 11023, conductors 460, e161 to ground at. the armature and front Contact; oit relay VJC31. Relay n'L03 in attracting its upper armature ren'ioves the bridge containing condenser 450 from across the talking circuit. The private branch change operator new bridges her head set (not shown) across the talking conductors 433, 409 and learns the number ol? the wanted line. She then inserts the other plug into' the jack of such line, and by means ot her ringing key not shown) signals such party. Upon his response, he is informed that the toll connection is now set up. malien the calling party restores his receiver, the operator at the private branch exchange out the plug 'from `the jack 444, which, in denergizing relay 4.22, lights the'lamp 439 at the niain office, whereupon the operator pulls out the plug 420 from jack 400 and the plug #i3-L from thetoll jack.

lVhile the retraction of the upper armature of relay A.l-flG removed ground from the third wir@ 404 the attraction of the armature of relay 452 rcapplied the same to maintain ground on the multiples 217 to cause the trunk to test busy as long as the plug at the private branch exchange remains in the jack. The trunk is also maintained busy .is long as the plug 420 remains `in jack 400 at the main o 'ee, since the rela`y 431 is during 'such period energized and at its right armature applies ground to the third wire 404.

What is claimed is: g

l. In a telephone exchange system, .the combination with telephone lines, senders therefor, a connecting circuit including atomatic switches, and a repeating relay` in saidl circuit operated by said senders Vto set said switches, of condensers in said connect,

ing circuit between said relay and switches, normally disconnectedv f rom the called end of the connecting circuit, and means/automatically actuated upon the response of the called party for connecting said condensers in circuit with the called line.

2. In a telephone exchange system, the combination with telephone lines, senders therefor, a connecting circuit including a'utomatic switches, a repeating relay in'said circuit operated by said senders toset said switches, and condensersin said connecting circuit between said relay and switches, of a side switch normally disconnecting said condensers from the called end of said connecting circuit, and means-operated .by the response of thc called party foivadvancing said-.side switch to connect said condensers in circuitwith the called line.

combination with telephone lines, senders therefor, a connecting circuit including automatic switches, a repeating relay in said circuit Operated by said senders to set said switclies, and condensers in said connecting circuit between said relay and switches, of' a` side switch normally disconnecting said condensers from the called end of said connecting circuit, a circuit for the escape magnet of said side switch whereby-the side switch is advanced to connect said condensers in circuit with the called line. a control relay for closingthe same, a side switch associated with the last of the train of automatic switches having a ringing 'and a talking position, means for advancing said side switch to the ringing position operated if the selected line is idle, a slowrelease relay, a circuit therefor closed in the ringing posisaid slow relay is opened, and a circuit including a,front contact of said slow relay andan armof said connector side switch in its fourth positionand saidcontrol relay to` i circuit operated\by said senders to set said switches,

- circuit between said relay and switches; of

an electromagnetic switch 'normally diggin.

`throulgh the .windings of said relay. tion, means operated'by the'responseof the 7. called party 'for advancing said switch to the talking position in which the circuit for and condensers in said connecting.

v relay vnecting said'condensers from the called end of the connecting'circuit, means o erated by the response of the called party or actuating said switch to interconnect the-calling and called ends throughsaid condensers, in- A d uctive means connected on both sides of the .open contacts of said electromagnetic switch, and means actuated by the busy condition of the selected line for rendering said inductive means effective to transmit a busy tone to the calling line.

5. In a telephone exchange system, the `combination with telephone lines, senders therefor, a connecting circuit including automatic switches, a repeating relay in said circuit operated-by said senders toset said switches, and condensers in said conductors between said relay and switches, of a side switch 'normally disconnecting at a pair of its arms said condensers from the called end, means operated by the response of the called party for advancing said 'side switch to interconnect the calling and called ends through said condensers, inductive means connected on both sides of said\side switch-arms, a source .of busy-tone `current, and means actuated by the busy I condition of the selected line for transmitting a tone from salid source around j said side-switch arms to the calling line. In a telephone exchange system, the

- nected on each side of said side-switch arms,

means operated by the response of the called party for advancing said side switch to inter-connect the calling and called ends of the vioo connecting circuitv through said condensers and for connecting said relay in circuit? with the' called line, a source of busy-tone current, and means actuated by the busy condition ofthe selected line for transmitting a tone from said source around said sideswitch arms'to the calling line by induction n a telephone exchange system, the combination with telephone lines, a repeating relay set, condensers and a selector, a sids switch adapted inv one position to feed current to the calling line through the windings of one of said relays, and in anothe to cutoff said relay and condensers and extland the callingv line directl to the selector brushes, groups ef trun s terminating in said selector, means `for setting u p a connection between said lines including one of said trunks, and means controlled by the selection of a predetermined trunk group for causing said side switch to cut olf said and condensers, and feed current to the callingv line'over the seized trunk.

` tomatic switches, groups of manual switches,

some `of said trunk groups terminating in 'said automatic switches and some. in said manual switches, means for setting said selector upoii an idle trunk in any group, signals associated with said manual switches, means operated upon the actuation of a manual switch in response to the signal .thereof for excluding said feed coil and condensers, and means for feeding current to the calling line over said manual switch.

9. In a telephone exchange system, the conibination with a plurality of oflices, telephone lines terminating therein, a connecting circuit at one of said offices including a battery feed coil, condenser, and a selector, a side switch adapted in one position to feed current tothe calling line through the windings of said feed coil and in another to cut ctl-l said coil and condensers and extend the calling lines` directly to the selector brushes, groups of trunks terminating in said selec tor, means including saidV selector for setting up a connection including two lines in the saine office, and means for causing said selector to pick out a trunk leading to the distant office, a circuit for advancing said side switch to cut off said condensers, a re lay adapted to` be operated to prepare said circuit-When a trunk to the distant oiiice is selected, and means operated when said connection is `established with the distant oii'ice for closing said circuit.

10. In a telephone exchange system, theV combination with a plurality of offices, telephone lines terminating therein, a connecting circuit at one of said oifices including a battery feed coil, condenser, and a selector, a side switch adapted in one position to feed current to the calling line through the windings for said feed coil and in another to cut off said coil and condensers and extend the calling lines directly to the selectorbrushes, groups of trunks terminating in said selector, means including said selector Vfor set'- ting `up a connection including two lines in the same office, and means for causing said selector to pick out a trunk leading to the distant office, a circuit for advancing said sido switch to cut off said condenser, a relay, lmeans including an auxiliary switch copies ot this patent may be obtained for rfive cents each, by addressing 'che "Commissioner of Patents.

Washington, D. C.

closing said circuit, and a circuit for said` second relay closed 'whenV the connection is established with the distant oiiice for operating said second relay. i 11. In a telephone exchange system, the combination with an automatic office, a manual office, telephone lines teiiiiinating therein, a connecting circuit including a feed coil, condensers, and a selector in said automatic oflice,means including said selector for setting up a connection in said automatic office for causing said selector to pick out a trunk leading tothe manual office, a signal thereat operated upon the seizure of an idle trunk, a side switch adapted in one position to feed current to the calling line through the windings of said feed coil and in another to cut oif said coil and condensers and extend the calling line directly to the selector brushes, and manual means associated with the's'e'ized trunk at the manual office andactuated in response to said signal for causing said side switch to cut off said coil and condensers, and vfeed current to the calling line over the seized trunk.

l2. ln a telephone exchange system, the comhination with an automatic office, a manual office, telephone lines terminating therein, a connecti u g circuit including an impulse relay, condensers, and a selector in said automatic office, trunks terminating therein leading to said manual office, means including said impulse relay and selector for setting up a connection in said automatic office or causing said selector to pick out one of said trunks leading to the manual office, a side switch adapted in one position to feed current to the calling line through the windings of said impulse relay and in another to cut off said coil and condensers and extend the calling line directly to the selector brushes, a circuit for advancing said side switch to cut of said condensers, a relay adapted to be operated to prepare said circuit when said trunk is selected, and means controlled by the operator at the manual office for closing said circuit and for feeding current to the calling line over the seized trunk.

In Witness whereof, we hereunto subscribe our names this 8th day of March, A. D.

SAMUEL B. WILLIAMS, Jia. ARTHUR B. SPERRY. 

